Day 1
AT HOME
Read pages 236-244
- Describe the main components of soil.
- Outline the storages, transfers, transformations, inputs and outputs within soil systems.
- Describe the soil horizons.
- What is soil texture? How do we determine a soil's texture?
- Compare the structure and properties of sand, clay and loam soils, including their effect on primary productivity.. Refer to the soil texture diagram.
IN CLASS
Soil Prelab
Soil Formation Factors
The complex nature of soil means that the type of soil that a region has depends on many factors. To see this, just look at the soils you find in different locations. Is the soil in the desert like that in a rainforest? Is the soil in Arctic regions like that near the equator? What about the soil on a mountain compared to that in a valley? These locations all have different soils because of a myriad of factors.
One of the most important factors is the type of rock from which the inorganic material in the soil originated. The parent rock provides the soil with a great deal of the chemical backbone for the soil. For instance, a soil that contains sediment from limestone will be high in calcium, and will also have a basic pH. This will be much different than one that derives from granite, which will have a higher sodium or aluminum content and a pH that tends more toward neutral or acidic.
The type of parent rock will also affect the soil in other ways. The grain size of the inorganic materials is also affected by the parent rock’s hardness, fracture characteristics, and the crystalline structure of any minerals in the rock. Rocks containing mica will produce small, flat grains like that found in clay, while rocks with a lot of quartz might produce rounder grains like that found in sand.
The climate of the region will also greatly affect this sedimentation process in several ways. Before the parent rock can become part of the soil, it must be broken down either physically or chemically. Rain, especially exceptionally acidic rain, will leach elements out of a rock, which moves them into the local soil as well as weakening the chemical bonds within the rock, making it more likely to fracture. Water and wind flowing across the rock can also physically breakdown the rock, as can ice that expands in cracks and pore spaces. The rain and wind also operate as erosional forces to move the weathered sediments to new locations.
Soils are constantly changing. However, before mankind became ubiquitous, this change was often gradual and slow. Today, human activity has become one of the greatest factors affecting a soil. We move large sections of sediments, we irrigate soils that never had water, and we change the organisms that live on and in the soil. We make molehills out of mountains, and vice versa.
1. What is leaching?
- Check your soil to see if it is dry.
- Crush any remaining clumps and try to turn your soil into a powder.
- Remove any remaining rocks or plant material.
- If your soil is dry, return it to the ziploc bag.
- Complete the reading and questions below on a sheet of paper (individually)
Soil Formation Factors
The complex nature of soil means that the type of soil that a region has depends on many factors. To see this, just look at the soils you find in different locations. Is the soil in the desert like that in a rainforest? Is the soil in Arctic regions like that near the equator? What about the soil on a mountain compared to that in a valley? These locations all have different soils because of a myriad of factors.
One of the most important factors is the type of rock from which the inorganic material in the soil originated. The parent rock provides the soil with a great deal of the chemical backbone for the soil. For instance, a soil that contains sediment from limestone will be high in calcium, and will also have a basic pH. This will be much different than one that derives from granite, which will have a higher sodium or aluminum content and a pH that tends more toward neutral or acidic.
The type of parent rock will also affect the soil in other ways. The grain size of the inorganic materials is also affected by the parent rock’s hardness, fracture characteristics, and the crystalline structure of any minerals in the rock. Rocks containing mica will produce small, flat grains like that found in clay, while rocks with a lot of quartz might produce rounder grains like that found in sand.
The climate of the region will also greatly affect this sedimentation process in several ways. Before the parent rock can become part of the soil, it must be broken down either physically or chemically. Rain, especially exceptionally acidic rain, will leach elements out of a rock, which moves them into the local soil as well as weakening the chemical bonds within the rock, making it more likely to fracture. Water and wind flowing across the rock can also physically breakdown the rock, as can ice that expands in cracks and pore spaces. The rain and wind also operate as erosional forces to move the weathered sediments to new locations.
Soils are constantly changing. However, before mankind became ubiquitous, this change was often gradual and slow. Today, human activity has become one of the greatest factors affecting a soil. We move large sections of sediments, we irrigate soils that never had water, and we change the organisms that live on and in the soil. We make molehills out of mountains, and vice versa.
1. What is leaching?
Soil Texture
Soil can be classified with the use of a soil textural triangle. The relative proportions of particle sizes that make up the soil determine soil texture. The particles, from smallest to largest, are clay, silt, and sand.
Soil can be classified with the use of a soil textural triangle. The relative proportions of particle sizes that make up the soil determine soil texture. The particles, from smallest to largest, are clay, silt, and sand.
2. Use the soil textural triangle shown above to complete the data table. Record the % of particles and the names of their textures.
Porosity and permeability
Soils are made of particles of different types and sizes. Related to a soil's texture is the amount of space between particles (porosity) and the ease at which gases and liquids can pass through the soil (permeability). The space between the particles is called pore space. The porosity of a rock is determined by the amount of water it is able to hold. Materials that have lots of spaces between the particles have a high porosity. The ability of a rock or earth material to transmit a fluid is known as permeability. If the particles fit tightly together and do not allow water to move through them at all, the rock or soil is said to be impermeable.
Soils with a very fine clay particle texture have lots of micropores. This results in a large porosity made up of many microscopic pores but a low permeability. In contrast sandy soils have fewer macropores with a smaller total space, but the larger spaces allow sandy soils to drain well.
The low permeability of clay means that it can also lock dissolved minerals between the pores making it hard for plant roots to access. Strangely the result can be a soil that is rich in minerals but has low fertility.
3. Which sample is the most permeable? Explain.
4. Which sample is the least permeable? Explain.
5. Why do clay soils have low fertility?
Soils are made of particles of different types and sizes. Related to a soil's texture is the amount of space between particles (porosity) and the ease at which gases and liquids can pass through the soil (permeability). The space between the particles is called pore space. The porosity of a rock is determined by the amount of water it is able to hold. Materials that have lots of spaces between the particles have a high porosity. The ability of a rock or earth material to transmit a fluid is known as permeability. If the particles fit tightly together and do not allow water to move through them at all, the rock or soil is said to be impermeable.
Soils with a very fine clay particle texture have lots of micropores. This results in a large porosity made up of many microscopic pores but a low permeability. In contrast sandy soils have fewer macropores with a smaller total space, but the larger spaces allow sandy soils to drain well.
The low permeability of clay means that it can also lock dissolved minerals between the pores making it hard for plant roots to access. Strangely the result can be a soil that is rich in minerals but has low fertility.
3. Which sample is the most permeable? Explain.
4. Which sample is the least permeable? Explain.
5. Why do clay soils have low fertility?
Soil Nutrients
Plants need food (nutrients) for healthy growth. Nitrogen, Phosphorus and Potash (N, P and K for short), play a vital role in plant growth just as vitamins, minerals, carbohydrates and protein do in our health.
N – Nitrogen is synonymous with plant nutrition. It is directly responsible for producing leaf growth and green leaves. A deficiency causes yellow leaves and stunted growth. Too much nitrogen causes overabundant foliage with delayed flowering; the plant becomes subject to disease and its fruit is of poor quality.
P – Growing plants need phosphorus. It is the major constituent of plant genetics and seed development. A deficiency causes stunted growth and seed sterility. Phosphorus aids plant maturity, increases the seed yield, increases fruit development, increases vitamin content and aids the plant’s resistance to disease and winterkill.
K – Potash strengthens the plant. It helps form carbohydrates and promotes protein synthesis. It will improve the color and flavor of fruit. It further aids early growth, stem strength and cold hardiness. Plants deficient in potash are usually stunted and have poorly developed root systems. Leaves are spotted, curled and appear dried out at the edges. Yields for potash deficiency are low.
All fertilizer labels have three bold numbers. The first number is the amount of nitrogen (N), the second is the amount of phosphate (P2O5) and the third is the amount of potash (K2O). This label, known as fertilizer grade, is a national standard. A bag of 10-10-10 fertilizer contains 10% nitrogen, 10% phosphate, and 10% potash.
To calculate the pounds of nitrogen in a 50-lb bag of 10-10-10 fertilizer, multiply 50 by 0.10. A 50-lb bag contains a total of 15 lbs of nutrients: 5 lbs N, 5 lbs P, and 5 lbs K. The remaining weight is filler, usually sand or granular limestone.
6. In the bag of fertilizer below, how many pounds of nitrogen are there?
7. How many pounds of Phosphate?
8. How many pounds of Potash?
Plants need food (nutrients) for healthy growth. Nitrogen, Phosphorus and Potash (N, P and K for short), play a vital role in plant growth just as vitamins, minerals, carbohydrates and protein do in our health.
N – Nitrogen is synonymous with plant nutrition. It is directly responsible for producing leaf growth and green leaves. A deficiency causes yellow leaves and stunted growth. Too much nitrogen causes overabundant foliage with delayed flowering; the plant becomes subject to disease and its fruit is of poor quality.
P – Growing plants need phosphorus. It is the major constituent of plant genetics and seed development. A deficiency causes stunted growth and seed sterility. Phosphorus aids plant maturity, increases the seed yield, increases fruit development, increases vitamin content and aids the plant’s resistance to disease and winterkill.
K – Potash strengthens the plant. It helps form carbohydrates and promotes protein synthesis. It will improve the color and flavor of fruit. It further aids early growth, stem strength and cold hardiness. Plants deficient in potash are usually stunted and have poorly developed root systems. Leaves are spotted, curled and appear dried out at the edges. Yields for potash deficiency are low.
All fertilizer labels have three bold numbers. The first number is the amount of nitrogen (N), the second is the amount of phosphate (P2O5) and the third is the amount of potash (K2O). This label, known as fertilizer grade, is a national standard. A bag of 10-10-10 fertilizer contains 10% nitrogen, 10% phosphate, and 10% potash.
To calculate the pounds of nitrogen in a 50-lb bag of 10-10-10 fertilizer, multiply 50 by 0.10. A 50-lb bag contains a total of 15 lbs of nutrients: 5 lbs N, 5 lbs P, and 5 lbs K. The remaining weight is filler, usually sand or granular limestone.
6. In the bag of fertilizer below, how many pounds of nitrogen are there?
7. How many pounds of Phosphate?
8. How many pounds of Potash?
Soil pH
The hydrangea is a bush with snowball-like flowers on it. When a hydrangea grows on the East Coast, the flowers are blue. When that same kind of hydrangea grows in the Midwest, the flowers are pink. What causes the flowers to be two different colors? The answer is the soil. In much of the East Coast, the soil is acidic. In the Midwest, some of the soil is alkaline—it has more calcium in it than acidic soil does.
Some plants grow best in fairly acidic soil—blueberries, cranberries, and pineapples, for example. Other plants, like cotton and alfalfa, need a soil that is neutral—neither acidic nor alkaline. Most plants seem to do well in a mildly acidic soil.
Material can be added to soil to make it the right acidity for the crop that will be grown. To know what and how much material to add, the soil has to be tested. Samples of soil are analyzed by a machine to measure a soil’s pH—the measure of how acidic or alkaline it is. Soil that has a pH between 0 and 7 is acidic, the lower the number, the more acidic the soil. Soil that has a pH of 7 is neutral. Soil that has a pH between 7 and 14 is alkaline, the higher the number, the more alkaline the soil. Actually, in nature, soils don’t seem to reach the extremes of 0 and 14. They range between about 3.5 and 11.
If the soil needs to be more alkaline, then lime—a chalky material containing calcium—is added to the soil. If the soil needs to be made more acidic, sulfur can be added to the soil. Most of the time, the soil needs to be made more alkaline rather than more acidic.
9. How would you classify soil that has a pH of 8?
10. Suppose a soil has a pH of 5.5, but you want to grow cotton. What would you do?
The hydrangea is a bush with snowball-like flowers on it. When a hydrangea grows on the East Coast, the flowers are blue. When that same kind of hydrangea grows in the Midwest, the flowers are pink. What causes the flowers to be two different colors? The answer is the soil. In much of the East Coast, the soil is acidic. In the Midwest, some of the soil is alkaline—it has more calcium in it than acidic soil does.
Some plants grow best in fairly acidic soil—blueberries, cranberries, and pineapples, for example. Other plants, like cotton and alfalfa, need a soil that is neutral—neither acidic nor alkaline. Most plants seem to do well in a mildly acidic soil.
Material can be added to soil to make it the right acidity for the crop that will be grown. To know what and how much material to add, the soil has to be tested. Samples of soil are analyzed by a machine to measure a soil’s pH—the measure of how acidic or alkaline it is. Soil that has a pH between 0 and 7 is acidic, the lower the number, the more acidic the soil. Soil that has a pH of 7 is neutral. Soil that has a pH between 7 and 14 is alkaline, the higher the number, the more alkaline the soil. Actually, in nature, soils don’t seem to reach the extremes of 0 and 14. They range between about 3.5 and 11.
If the soil needs to be more alkaline, then lime—a chalky material containing calcium—is added to the soil. If the soil needs to be made more acidic, sulfur can be added to the soil. Most of the time, the soil needs to be made more alkaline rather than more acidic.
9. How would you classify soil that has a pH of 8?
10. Suppose a soil has a pH of 5.5, but you want to grow cotton. What would you do?
11. Outline the transfers, transformations, inputs, outputs, flows and storages within soil systems by drawing a systems diagram.
Storages:
Storages:
- organic matter
- organisms
- nutrients
- minerals
- air
- water
- biological mixing
- leaching
- decomposition
- chemical weathering
- nutrient cycling
- leaf litter (organic)
- parent material (inorganic)
- precipitation (inorganic)
- energy
- uptake by plants
- soil erosion